The first total solar eclipse to sweep the U.S. from coast to coast in 99 years plunged broad swaths of the nation into darkness, putting more than 12,000 megawatts of solar power at risk. And the lights were still on.

The grid operator in California, home to more solar power than any other state, reported “absolutely no problems” and said fewer supplies went offline than expected.

“It’s been smooth sailing,” said David Shepheard, managing director at consultant Accenture. “Everyone I talked to so far said there were no unexpected impacts. All of the industry folks were saying it’s a good dress rehearsal.”

The eclipse represented the first major test of the power grid since America started bringing large amounts of intermittent solar and wind resources onto the system. Solar installations have grown ninefold since 2012 and renewable sources are forecast to supply just as much of America’s electricity demand as natural gas by 2040.

“It was similar to the fog coming into San Francisco,” said Audrey Lee, vice president of grid services at Sunrun Inc., the largest independent U.S. residential solar company. She earlier said that any impact would be manageable.

Regional grid operators from California to Pennsylvania planned to provide real-time updates on how their networks were handling fluctuating power flows as millions of Americans headed outside to gaze at the sky.

The celestial event provided an opportunity to test plants, software and markets refined in recent years in anticipation of the day when renewable energy becomes the dominant source of power. Bloomberg New Energy Finance has projected that renewables will supply more than half of the world’s electricity in 2040.

The Bonneville Power Administration reported no impact to the Northwest’s electric solar grid from the eclipse.

“We have very little solar generation,” said Kevin Wingert, a BPA spokesman.

There are a few 1 to 5 megawatt solar facilities in the region, but their output pales in comparison to the electric output from hydropower dams, he said.

BPA has been planning for the influx of visitors to view the eclipse in Oregon and Idaho for several months. Where possible, crews doing maintenance were shifted out of the zone of totality this week. BPA officials also were concerned that visitors to national forests might camp out under high voltage transmissions lines, considering the clearings a good place to view the eclipse.

“We’ve had no incidents to date,” Wingert said late Monday afternoon.

California tapped into its network of hydropower generators and gas plants that can ramp up quickly. The state also embarked upon a public relations campaign to convince residents to conserve energy to minimize greenhouse-gas emissions while solar plants are down.

About 3,400 megawatts of large-scale solar came off the system during the eclipse, according to Nancy Traweek, executive director of system operations for the California Independent System Operator. That was less than the forecast of 4,600 megawatts.

“Things went really, really well,” Eric Schmitt, vice president of operations for CAISO, told a press briefing. “We’re very pleased with the outcome.”

Spot wholesale prices at Northern California’s NP15 hub fell as the eclipse started and passed, touching a low of minus $15.84 a megawatt-hour at 11:35 a.m. local time as solar started coming back up, according to grid data compiled by Bloomberg. Spot electricity averaged $21.50 from 10 a.m. to 11 a.m., less than half that for supplies secured in advance for the same hour in the day-ahead market.

“They have too much generation in the marketplace and they are paying people to take electricity off of the wholesale market,” Shepheard said about the negative prices.

U.S. utility owner Southern Co. marked the occasion by offering special deals on energy saving and smart-home products through its Georgia Power unit.

In North Carolina, Duke Energy Corp. expected about 2,000 megawatts, or 80 percent, of utility-scale solar farms to go offline.

Most areas got a pretty good view for an eclipse in the middle of a summer’s day, said Brendon Rubin-Oster, a meteorologist with the U.S. Weather Prediction Center in College Park, Maryland. Kansas City and parts of Missouri may have been the worst places to see the spectacle, as there was a lot of cloud cover.

Despite the country’s focus on the sun, it wasn’t the best day for solar stocks. Canadian Solar Inc. slumped 9.9 percent to $14.99 after being downgraded by Barclays Plc. First Solar Inc. fell 4.4 percent to $45.96 and SunPower Corp. declined 4.3 percent to $8.84.